Arrows with full color: leave Arrows(observer) OFF and rotate Env Yaw/Pitch to aim the studio's dark zone — that forms the arrows from the real environment (the reference's method).
Gem Brightness1.00
Dark Lift0.00
Reference (WebGI) defaults: 5 bounces · 0.01 dispersion · 0.3 Fresnel · 0.5 Normal Smooth · 0.98 Squash. Normal Smooth tames the "shattered glass" facets; Fresnel adds bright facet highlights.